The present invention pertains to ties that are useful for forming a loop for retaining a bundle of elongated articles, such as cables and is particularly directed to an improvement in the abutment wall in the locking head of such ties. Such a tie is commonly known as a cable tie
One type of tie 10, as shown in FIGS. 1, 2 and 3, includes an elongated tongue 12 with two ends and two broad sides 14, 16, a locking head 18 at one end of the tongue, a tip 20 at the other end of the tongue 12 and a set of ratchet teeth 22 extending along one broad side 14 of the tongue 12, wherein the locking head 18 has sides defining an opening 26 for receiving the tip 20 of the tongue 12. The sides include a movable pawl 28 that is hinged at one side of the opening 26 and an abutment wall 30 that is across the opening 26 from the pawl 28. The pawl 28 has pawl teeth 32 disposed for locking engagement with the set of ratchet teeth 22 when the tip 20 of the tongue 12 has been inserted through the opening 26 with the ratchet teeth 22 facing the pawl 28. When at least one pawl tooth 32 is so engaged, the pawl 28 is movable toward the abutment wall 30 in response to a pulling force applied to the tongue 12 in a direction opposite to the direction of insertion 34 in order to force the tongue 12 against an abutment surface 36 of the abutment wall 30. Such ties typically are made by injection molding plastic material into a mold defining cavities for forming the ties.
A problem arises incident to the use of the type of tie described above in that, if the pulling force applied to the tongue 12 in the direction 34 opposite to the direction of insertion 34 is too large, the pawl 28, which is in locking engagement with the ratchet teeth 22 on the tongue, is pulled toward the abutment wall 30 with such force as to cause the abutment wall 30 to bow outward, as shown in FIGS. 4 and 5. Consequently, when the abutment wall 30 bows outward, the pawl 28 continues to move toward the abutment wall 30 and eventually rotates about the hinge to such an extent that the pawl teeth 32 become disengaged from the ratchet teeth 22 and the tongue 12 is pulled out of the locking head 18. One solution to this problem is to increase the thickness of the abutment wall. However, this solution has the disadvantages of increasing the material in and thereby the unit cost of the tie and of subjecting the abutment wall of an injection molded tie to deformation when the injected plastic material cools.